All things freshwater: news, analysis, humor, reviews, and commentary from Michael E. 'Aquadoc' Campana, hydrogeologist, hydrophilanthropist, Professor of Hydrogeology and Water Resources Management in the Geography Program of the College of Earth, Ocean, and Atmospheric Sciences (CEOAS) at Oregon State University, Emeritus Professor of Hydrogeology at the University of New Mexico, Past President of the American Water Resources Association and Past Chair of the Scientists & Engineers Division of the National Ground Water Association. He is founder and president of the nonprofit Ann Campana Judge Foundation, an organization involved with WaSH (Water, Sanitation, and Hygiene) in Central America. He serves on the Steering Committee of the Global Water Partnership (GWP). CYA statement: the opinions expressed herein are solely those of Michael E. Campana and not those of CEOAS, Oregon State University, ACJF, AWRA, NGWA, GWP, my spouse Mary Frances, or any other person or organization.

Texas Agriculture Law BlogDon't let the name fool you - there are lots of water issues in agriculture and Tiffany Dowell of Texas A&M University does a fabulous job with this important Internet resource. Give it a read - I do every day!

The Way of WaterOregon State University Geography PhD Student, Jennifer Veilleux, records her fieldwork, research, and thoughts about transboundary water resources development in the Nile River and Mekong River basins. Particular attention is given to Ethiopia's Grand Ethiopian Renaissance Dam and Laos' Xayaburi Dam projects.

Thirsty in SuburbiaGayle Leonard documents things from the world of water that make us smile: particularly funny, amusing and weird items on bottled water, water towers, water marketing, recycling, the art-water nexus and working.

This Day in Water HistoryMichael J. 'Mike' McGuire, engineer extraordinaire, NAE member, and author of 'The Chlorine Revolution', blogs about historical happenings in the fields of drinking water and wastewater keyed to calendar dates.

Watering the DesertAptly-titled blog by CJ Brooks, a lawyer-hydrologist-geologist from Tucson, AZ.

Watershed Moments: Thoughts from the HydrosphereFrom Sarah Boon - rediscovering her writing and editing roots after 13 years, primarily as an environmental scientist. Her writing centres around creative non-fiction, specifically memoir and nature writing. The landscapes of western Canada are her main inspiration.

Sunday, 24 February 2008

Stationarity is Dead! Whither Water Management?

Last summer Chris Milly wrote an articlein which he proclaimed "Stationarity is dead!" I noted that we hydrologists have been reluctant to admit that because it would cast doubt on the way we manage water. I commented to a colleague that when I took the late Chester Kisiel's statistical hydrology course on the early 1970s, he discussed why hydrologic stationarity was an invalid concept. Then we proceeded to apply techniques that assumed stationarity to solve water management problems - dam design, etc.

Milly and his colleagues recently published a longer article in Science:

By "stationarity" we mean, that, statistically speaking, the future looks like the past - whether we are talking about precipitation, runoff, or other flows in the hydrologic cycle, depicted below. The numbers represent relative flow rates (from Hornberger et al., 1998, Elements of Physical Hydrology).

Take this frequency diagram (again, from Hornberger et al., 1998, Elements of Physical Hydrology). It shows the frequencies of annual precipitation in Seattle and Denver.

Stationarity says we can assume that the mean annnual precipitation in Seattle and Denver over the next 50 years, 1990-2039, would be "around" 941 mm and 380 mm, respectively - the same as 1940-1989. In fact, by invoking the stationarity assumption we can assume that over the next few thousand years (or longer), the rainfall distributions for Seattle and Denver will look the same as they do above.

The same would hold for the distribution of runoff (streamflow), which can also be described by frequency or probability distrbutions.

This assumption makes planning easier. For example, if we need to know runoff so that we can design a large enough dam or big enough reservoir to provide enough water or flood protection for the next 100 years, stationarity allows us to do that with some degree of confidence, provided we have enough data to construct or develop a frequency or probability distiribution.

We know that hydrologic processes do not behave like stationary ones. Why not? Well, we humans have altered the hydrologic cycle. Example: imagine your watershed and what it looked like 200 years ago, or even 20 years ago. It has probably seen much development, which has changed the rainfall-runoff relationship. So if a dam in your watershed was built 50 years ago, the runoff frequency distribution upon which it was based probably is invalid.

Milly et al. argue that climate change is rendering hydrologic stationarity a quaint concept, and we are grasping for ways to translate observations into predictions. So we are now likely dealing with a nonstationary process - the mean precipitation (or runoff, etc.) in the future won't be the same as it was in the past. So how do we plan?

Global warming will alter runoff patterns. The figure below, from Milly et al.), shows the "winners" and "losers" (median values from 12 climate models) in the volume of runoff from ice-free areas in the mid-21st century, relative to the 1900-1970 period. What you see is nonstationarity: the future is not like the past.

The reds and yellows indicate the greatest percentage decrease.

Look at Mexico, the Southwest USA, parts of Europe, northern and southern Africa, and the Middle East. Could be ugly.

Milly et al. indicate the critical need to develop new probabilistic models for rainfall, streamflow, etc. that are nonstationary.

The hydroclimatologic future is upon us, and we are unprepared.

"Statistics always remind me of the fellow who drowned in a river whose average depth was only three feet." -- Woody Hayes, ex-Ohio State football coach

Circle of BlueCircle of Blue uses journalism, scientific research, and conversations from around the world to bring the story of the global freshwater crisis to life. Here you’ll find new water reports, news headlines, and hear from leading scientists.

Drink Water For LifeThe idea is simple. Drink water or other cheap beverages instead of expensive lattes, sodas, and bottled water for a set period of time. A day, a week, a month, Lent, Ramadan, Passover, or some other holiday period.

eFlowNet NewsletterFrom the International Union for the Conservation of Nature (IUCN) this newsletter has lots of information about environmental flows and related issues.

Sustainable Water Resources RoundtableSince 2002, the Sustainable Water Resources Roundtable (SWRR) has brought together federal, state, corporate, non-profit and academic sectors to advance our understanding of the nation’s water resources and to develop tools for their sustainable management.